fix luks header backup to properly detect partitions

previously the code was modeled off of the partition backup methodology, this resulted in the code only attempting to detect luks on actual devices, and not on partitions. The code would step through every disk on the system (sda, sdb, etc.) and do a 'cryptsetup isLuks' on that device, and then based on that output save the luks header for any device that had one. Unfortunately, in many cases, luks headers are found on the partitions of those disks. So we were failing to detect any luks partitions and thus failing to backup their luks headers.

this commit changes that, it now will look for luks headers on the devices themselves (for cases where a full disk is used without partitions), and on any partitions that are detected